A set of comprehensive neuropsychological test batteries is used to provide a complete assessment of various cognitive and sensory functions that can be related to damage or dysfunction in different regions of the brain. The adult battery comprises tests designed to lap the following aspects of behavior, attention, executive functions, language, memory, motor functions, orientation, selected sensory and perceptual functions, vigilance and visual-spatial functions. In addition, adults are given a test of general intelligence and. In some studies, subjects are administered a structured psychiatric interview. Modified batteries have been developed for the assessment of infants, preschool children, and children ages 6-16. The data provided by these batteries are being used to construct a neuropsychological theory of the elements of attention that may be applied to the neurological and psychiatric diagnostic groups under study in the LPP. The LPP has as it's major focus disorders involving impaired attention, including schizophrenia, epilepsy, head injuries and other factors that impair normal development, including malnutrition, parasite infection of the brain, and genetic influence, Comparisons are being carried out between the neuropsychological profiles of various groups of psychiatric patients and those of patients with known cerebral lesions in specified brain regions. Our data are being used to delineate neurobehaviorally-defined subgroups within diagnostic categories, an undertaking aimed at reducing variability in psychiatric diagnosis, treatment, and outcome. The data provided by this protocol provide a complete behavioral assessment that may be integrated with concurrently gathered electrophysiological, neuroradiological, and biochemical information.